DCC++ over WiFi issues

miniThrottle: A model railroad WiFi throttle.

An issue using the WiFi interface of DCC++

When using the WiFi interface of DCC++ and using DCC++ protocol, it appeared some packets were either being dropping or scrambled. The JMRI protocol over this interface appeared more reliable, but less feature rich than miniThrottle to DCC++. The examples below were a result of sending a status command to DCC++ over WiFi from miniThrottle console a few seconds apart. A further issue was found when DCC++ rebooted unexpectedly when using DCC++ over WiFi.

In the illustrations below the commands run at the console have no prefix, while outgoing packets are prefixed with "-->" and incoming packets are prefixed with "<--". In the unexpected interaction it looks like the data is all there but out of sequence, as if there are 2 separate streams of data being returned to miniThrottle.

Expected interaction

showpackets
sendcmd <s>
--> <s>
<-- <p1>
<-- <iDCC-EX V-4.0.1 / MEGA / STANDARD_MOTOR_SHIELD G-a26d988>
<-- <H 20 0>
<-- <H 21 0>
<-- <H 22 0>
<-- <H 23 0>
<-- <H 24 0>
<-- <H 25 0>

Unexpected interaction

showpackets
sendcmd <s>
--> <s>
<-- <p1>
<-- <iDCC-EX V-4.0.1 / MEGA / STANDTRSIL -2d8>
<-- ARD_MOO_HEDGa698
<-- <H 20 0>
<-- <  >
<-- H210
<-- <H 22 0
<-- <H 2 >
<-- 30
<-- <  >
<-- H240
<-- <H2 >
<--  50

A few options are worth trying:

Only use the DCC++ WiFi interface with JMRI protocol.
Upgrade DCC++ to the latest version. There may be a bug fix for the issue being experienced.
Replace the WiFi module with a WiFi serial interface. This would offload network processing from DCC++ to the serial module. An interesting candidate is https://github.com/AlphaLima/ESP32-Serial-Bridge. The port speeds would need to adjusted to match those of DCC++, but it would allow up to 3 WiFi throttles to be assigned to a dedicated serial port. In config.h of CommandStation-EX, look for the defines to enable the additional ports:
```
$ diff config.example.h config.h
// Around line 59
#define ENABLE_WIFI false
// Around line 124
#define LCD_DRIVER  0x27,16,2
// Around line 195, assuming you will use these for the "AlphaLima Serial" connections.
#define SERIAL1_COMMANDS
#define SERIAL2_COMMANDS
#define SERIAL3_COMMANDS
```
Skip WiFi altogether, assign two pins on the Esp32 to a Tx and Rx port and connect directly to serial on the DCC++ Arduino. This is an attractive option where just a single panel mounted miniThrottle is driving DCC++. No WiFi connectivity is required for this, and it is a build option available from miniThrottle version 0.4 onwards. Another feature of a WiFi free option, is it allows lower CPU speeds to be selected. Hardware dependant this can be as low as 10 MHz. WiFi requires 80 MHz or higher processor speeds to be selected.

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